In a weaving operation it is important that the heald shafts of the loom are properly connected to the heald shaft drives in order to assure the proper formation of the loom shed during weaving. Similarly, it is necessary to efficiently disconnect the heald shafts from the heald frame drive when a weaving harness is to be exchanged. For this operation it is necessary that each individual heald shaft is either disconnected or again connected with a drive rod on the outer right side and on the outer left side of the respective heald shaft.
German Patent Publication (DE-OS) 2,656,380 discloses an apparatus for connecting the heald shafts with the drive mechanism of a loom. The problem of connecting and disconnecting has been solved in this publication in that the drive rods are provided with claws in the area where they are to be connected with the heald shafts and in that a spacing is formed between the two rod sections that are made of spring material. An operating key is passed through this spacing after the locks of all heald shafts and the respective control elements are at least aligned in a row so that all heald shafts are at the same level. This operating key has an elliptic cross-section.
By operating said operating key, the drive rods are temporarily spaced apart in order to decouple the heald shafts from the drive rods or drive pulls.
Such an apparatus is effective for its purpose. However, the known apparatus requires a substantial effort for the leveling of the heald shafts and this effort is quite time consuming, especially when the loom comprises a large number of heald shafts. Even if the number of heald shafts is relatively small, the required precautions or rather efforts for the decoupling also do not appear to be in any useful relationship if compared with other measures for the decoupling. Another drawback of the known apparatus is seen in that it requires additional features in the loom, such as support bearings in front of and behind of the heald shafts for guiding the operating key.
Further, operating such a key is difficult because the clamping connections between the drive rod and the heald shaft are located in an area of the loom that is difficult to access by an operator. Another problem resides in the fact that the operating key must be introduced from the rear of the loom, namely from the side of the warp beam. Thus, introducing the operating key into the opening formed between the two clamping cheeks or jaws, may result in damage to the warp threads.